We use this expression to say that we are in control of something.
You can use this phrase in ………… language.
A: How are you managing with writing all those companies?
B: I’m on top of it now. I should finish in a couple of days.
A: Have you found an answer to the problem with the coffee machine in the office?
B: Yes, I’m on top of it now. There was just a problem with the right kind of coffee.